1. Field of the Invention
The present invention is generally related to an air supply system for an internal combustion engine and, more particularly, to a system for attenuating the sound emanating from a compressor used in conjunction with a fuel injected internal combustion engine.
2. Description of the Prior Art
Those skilled in the art of internal combustion engines are aware of the use of compressors in conjunction with fuel injected systems, particularly direct fuel injected systems that inject a fuel/air mixture directly into the combustion chamber of the cylinders of the engine. Skilled artisans in the field of sound attenuation are familiar with the use of expansion chambers which represent one of the types of silencing elements utilized in both intake and exhaust systems. In its simplest form, the expansion chamber consists of an inlet pipe, an expansion in area, an empty chamber, a contraction in area, and an outlet pipe. The expansion chamber was analytically modeled in the early 1950""s for plane-wave propagation assuming linear acoustics with no flow. This analysis revealed that the expansion chamber""s transmission loss is a function of the area expansion ratio of the expansion chamber, defined as the area of the cross section of the expansion chamber divided by the area of the cross section of the inlet tube.
U.S. Pat. No. 5,733,106, which issued to Lee on Mar. 31, 1998, describes a suction muffler for a reciprocating compressor with external holes to reduce noise attenuation. The compressor includes a cylinder block disposed in a chamber formed by a casing. A piston is mounted for reciprocation in a bore of the cylinder block. A valved cylinder head is disposed at the end of the bore. The cylinder head conducts fluid to the bore. The fluid enters the casing through an inlet therein and travels through a suction passage formed by a suction muffler and then through a base muffler before entering the cylinder head. The suction muffler includes exterior holes for communicating the suction passage of the suction muffler with a chamber of the casing, to thereby reduce the suction load occurring at the bore and valve plate.
U.S. Pat. No. 3,864,064, which issued to Gannaway on Feb. 4, 1975, describes a suction muffler tube for a compressor. A gas compressor having a suction muffler assembly for attenuating both high and low frequency noise produced by the inlet valve of the compressor is described. It includes an inner suction tube extending from the compressor intake to a muffler and a bypass tube surrounding the suction tube with the bypass tube having bypass apertures in the upper end thereof, whereby the effective cross-sectional area of the suction intake tube may be reduced thereby attenuating low frequency noise while at the same time retained adequate gas inflow to the compressor intake.
U.S. Pat. No. 6,382,931, which issued to Czabala et al on May 7, 2002, describes a compressor muffler. A muffler assembly for muffling noises associated with a compressor is described. The muffler assembly is mounted on the compressor such that the two move as a solid body. The muffler assembly includes an intake having a hollow interior adapted to receive a first flow of gas from the ambient environment. A baffle disposed in the hollow interior of the intake restricts the flow of gas through the intake. In one embodiment, the baffle defines at least a portion of a plurality of fluid portals that separate the first flow of gas into a plurality of flows of gas as the gas passes from the first side of the baffle to a second side of the baffle. As a result, the first flow of gas is disturbed and noise from the compressor is thereby attenuated. In another embodiment, a plurality of baffles are disposed in the hollow interior of the intake to define a tortuous path for the flow of gas through the intake for attenuating noise.
U.S. Pat. No. 5,938,411, which issued to Seo on Aug. 17, 1999, describes a compressor noise reducing muffler. The muffler includes a base muffler for a suction muffler connected to an upper end of the base muffler. Gaseous coolant flows through the suction muffler and the base muffler and into a cylinder head of a compressor. The suction muffler defines a path of travel wherein all of the gaseous coolant flows vertically downwardly, then horizontally, and then vertically downwardly to the base muffler.
U.S. Pat. No. 6,238,258, which issued to Ozawa on May 29, 2002, describes a direct air fuel injected watercraft engine. A number of embodiments of personal watercraft having engines that employ fuel air injection systems is described. The fuel air injection system is protected from the water ingestion by placing its inlet in an area that will be above the water level regardless of whether the watercraft is operating upright or is inverted and during the transition between these positions. In addition, an arrangement is provided for cooling the air compression so as to improve efficiency.
U.S. Pat. No. 6,206,135, which issued to Kim et al on Mar. 27, 2001, describes a suction noise muffler for a hermetic compressor. A suction noise muffler for a hermetic compressor which is capable of enabling a smooth flow of a refrigerant gas and reducing a suction noise by forming a predetermined shaped refrigerant gas flow guide path and a plurality of noise reducing sections, which includes an upper casing having a rectangular outer wall and a plurality of inner walls arranged within the outer wall, and a lower casing whereby the upper casing is inserted into the lower casing, for thus forming a refrigerant gas flowing path and a plurality of noise reducing sections thereby when assembling the upper casing and lower casing.
U.S. Pat. No. 6,287,098, which issued to Ahn et al on Sep. 11, 2001, describes a muffler for a rotary compressor. The compressor includes a main bearing having a discharge passage for discharging compressed gas and a boss for inserting a motor shaft, the main bearing forming a component of a compression chamber, and a muffler having a boss hole for passing the boss of the main bearing and a discharge opening for discharging the compressed gas, the muffler mounted on the main bearing, wherein the discharge opening in the muffler is formed at least one in number inside the discharge passage in the main bearing, whereby attenuating a noise generated in operation of the rotary compressor.
U.S. Pat. No. 5,906,477, which issued to Kim et al on May 25, 1999, describes a suction noise muffler mounting apparatus for a hermetic compressor. An improved suction noise muffler mounting apparatus for a hermetic compressor is disclosed. It is capable of more simply mounting a suction noise muffler to a cylinder head, for thus reducing the number of fabrication processes and increasing the productivity of a hermetic compressor, which includes a suction noise muffler head having a protrusion having a predetermined height and formed on the upper surface thereof and integrally engaged to the upper end of the suction noise muffler, and a fixing member provided for mounting the suction noise muffler to a portion of the cylinder head.
U.S. Pat. No. 4,330,239, which issued to Gannaway on May 18, 1982, describes a compressor muffler. A muffler for a refrigeration gas compressor which is tuned such that the attenuation curve and the impedance curve cross the frequency access at the pumping frequency of the compressor so as to result in optimum sound attenuation for the higher frequencies with minimum impedance at the pumping frequency. The muffler comprises a housing having first and second compartments with an inlet tube in the first compartment adapted for connection to a compressor gas outlet line to permit gas flow from the compressor gas outlet into the first compartment. An elongated tube has a first section in the housing with an inlet in the first compartment, a second section in the housing with an outlet in the second compartment, with these sections being joined by a third curve section disposed entirely outside of the housing. An outlet from the second compartment leads to the exterior of the compressor housing.
U.S. Pat. No. 6,056,611, which issued to House et al on May 2, 2000, discloses an integrated induction noise silencer and oil reservoir. An oil reservoir is used as a sound attenuator in an outboard motor and is placed under the cowl of the outboard motor with the throats of the engine""s throttle bodies disposed between the oil reservoir and the engine itself. This allows the sound emanating from the throttle bodies to be attenuated by the oil reservoir which is cup-shaped to partially surround the throat of the throttle bodies. A plate member can be attached to a hollow wall structure in order to enclose a cavity therebetween. The structure therefore serves as an oil reservoir for the engine and also as a sound attenuating member.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
In certain applications of an air compressor in conjunction with a fuel injected internal combustion engine, the operation of the compressor generates a significant amount of noise. When used in a marine vessel to provide propulsion therefore, a marine propulsion system comprising an air compressor can produce sufficient noise to diminish the enjoyment of operating the marine vessel. It would therefore be significantly beneficial if a relatively inexpensive sound attenuation system could be provided to reduce the sound emanating from the air compressor of the engine.
An air supply system for an internal combustion engine, made in accordance with the preferred embodiment of the present invention, comprises a compressor having a suction port and a discharge port. It also comprises an air distribution manifold, such as an air rail, having an inlet connected in fluid communication with the discharge port of the compressor. It also comprises a discharge sound attenuator connected in fluid communication with an outlet of the air distribution manifold. The discharge sound attenuator comprises an inflow conduit, an outflow conduit, and a chamber connected in fluid communication between the inflow and outflow conduits. The chamber has a cross sectional area, measured in a plane which is perpendicular to the direction of fluid flow, which is greater than a cross sectional area of the inflow conduit, measured in a plane which is perpendicular to the direction of fluid flow.
In a particularly preferred embodiment of the present invention, it further comprises a pressure regulator connected in fluid communication with the outlet of the air distribution manifold. The pressure regulator has an exhaust port connected in fluid communication with the inflow conduit of the discharge sound attenuator. A flexible hose is connected in fluid communication between the exhaust port of the pressure regulator and the inflow conduit of the discharge sound attenuator. The outflow conduit of the discharge sound attenuator is connected in fluid communication with ambient air pressure.
In a preferred embodiment of the present invention, it further comprises a suction sound attenuator connected in fluid communication with the suction port of a compressor. The suction sound attenuator comprises an inflow port, an outflow port, and a cavity connected in fluid communication between the inflow and outflow ports. The cavity has a cross-sectional area, measured in a plane which is perpendicular to the direction of fluid flow, which is greater than a cross sectional area of the inflow port, measured in a plane which is perpendicular to the direction of flow.
In a preferred embodiment of the present invention, the inflow port is connected in fluid communication with ambient air pressure and the outflow port is connected in fluid communication with the suction port of the compressor. A filter medium is disposed within the cavity and the air distribution manifold is an air rail. The internal combustion engine is a fuel injected engine and, more particularly, in a preferred embodiment of the present invention, the internal combustion engine is a direct fuel injected engine. A filter element is disposed within the chamber.